Pole shader



Sept. l, 1936.

C. CHAPMAN POLE SHADE".

Filed Sept. 2l, 3.935

VP v QM n eHcwm VS W/Aw/m DS Rlwwmj h vJ Cb Patented Sept. 1, 1936 UNITED STATES PATENT CFFICE POLE SHADER Charles H. Chapman, Scotia, N. Y., assignor to General Electric Company, a corporation of New York My invention relates to pole shaders for alternating current electromagnetic devices and has for its object the provision of an improved longlife pole shader having good electrical characteristics.

Pole shaders heretofore generally used have been formed of copper or copper alloys such as brass. As is well understood in the art, it is important that the pole shader have a high electrical conductivity in order to provide a substantially out-of-phase ux. However, brass pole shaders in spite of their low conductivity have been found more satisfactory than `copper pole shaders, in many installations, because of the beti5 ter mechanical properties of brass.

In accordance with the usual practice, the pole shader is ordinarily mounted on the magnetic structure of the electromagnetic device adjacent the pole face, and consequently, the pole shader is subjected to severe stresses, due to the shock and the vibration incident to the blow imparted to the frame by the armature each time that the electromagnetic device is operated. It has been found that these stresses are of such magnitude that repeated operation of the electromagnetic device will cause failure of the pole shader by breakage after a limited number of operations. Since the pole shader is ordinarily countersunk within the pole face so as to be protected` from the direct blow of the armature, it is believed that this breakage is usually caused by mechanical fatigue of the material comprising the pole shader. Accordingly, the principal criterion as to the mechanical suitability of a material for pole shaders is the fatigue resistance of the material, and I have found that the life of a brass pole shader, especially when the pole shader is formed with a bent portion, is extremely limited. In accordance with my invention, the pole shader is formed of an alloy consisting principally of copper but containing a few per cent of beryllium. A pole shader formed of a copperberyllium alloy containing about 2.25 per cent of beryllium has been found to have good electrical properties and an extremely long life. Such an alloy, however, is relatively expensive because of the high percentage of beryllium, and at present I prefer to form the pole shader from an alloy consisting mainly of copper but containing a minor quantity of beryllium and the remainder of a metal having the eiective alloying characteristic of cobalt. The preferred alloy consists of about 97 per cent copper, about 2.6 per cent cobalt and about 0.4 per cent beryllium. For a more complete understanding of my invention, reference should now be had to the drawing in which Fig. l is an elevational view, partly in section, of an alternating current electromagnetic device provided with two pole shaders embodying my invention, and Fig. 2 is a perspective detailed view of one pole of the device shown in Fig. 1, with my improved pole shader mounted thereon.

Referring to the drawing, I have shown my invention as applied to pole shaders of the type described and claimed in Patent No. 1,491,386 issued April 22, 1924, to John B. Ford. As shown, the pole shaders I0 and II are mounted adjacent the pole faces of the laminated magnetic structure I2 of an operating electromagnet having 15 a winding I3 mounted on one of the poles of the magnetic structure. Associated with and forming a part of the magnetic structure, is an armature I4 which is supported in the cradle I5 so that the armature will accurately align itself with the pole faces of the magnetic structure. The cradle support I5 is pivotally mounted in a support I6 and adapted o operate a shaft Il to which switch mechanism or other devices to be operated by the electromagnet are connected. 25

As shown, the pole shader is provided with angularly disposed ears I8 which embrace the sides of the pole and provide means for holding the pole shader in place on the magnetic structure. Each of the ears I8 is provided with an 30 aperture through which an iron bolt or pin 20 is adapted to pass so as to hold the pole shader in position on the magnetic structure. This bolt 20 also serves to hold the laminations of the magnetic structure together. 35

As previously pointed out, the pole shaders I0 and I I in accordance with my invention are made of a copper-beryllium alloy consisting principally of copper but containing a minor quantity of beryllium. At present the preferred alloy con- 40 sists of about 97 per cent copper, about 2.6 per cent cobalt and about 0.4 per cent beryllium. It will of course be understood that these proportions may be varied somewhat, and it has been found that satisfactory results are obtained when 45 the proportion of cobalt falls within the range 0.5 per cent to 2.75 per cent, and the proportion of beryllium within the range 0.025 per cent to 0.75 per cent.

The preferred alloy is treated by heating it for 50 approximately one hour at approximately 900 C. and then quenching it in Water and thereafter subjecting it to cold rolling. The alloy is then further treated by reheating it to approximately 500 C. for one or two hours, and then allowing 55 it to cool. The rate of cooling from the 500 C. temperature seems to be immaterial, and accordingly, air cooling is preferably used.

When thus treated the alloy has a conductivity between and 55 per cent that of copper and a Brinell hardness of about 240 as compared with an average hardness of about 35 for cast copper and for drawn copper. A standard brass commonly used for pole shaders has a conductivity of about 20 per cent that of copper and a Brlnell hardness or" about 100. It will thus be seen that pole shaders formed in accordance with my invention have a relatively high conductivity and are relatively hard and wear resistant. In addition, l have found that the alloy has a very high fatigue resistance.

The alloy is readily machinable and capable of being forged, and rolls readily at 850 C. It also rolls cold after quenching, and accordingly, it may readily be formed into pole shaders of any desired shape and size. For a further description of this alloy, reference may be had to Patent No. 1,847,929 issued March l, 1932 to Otto Dahl.

By actual test it has been found that the average life of a pole shader formed from brass and having the shape shown in the drawing is approximately 150,000 operations of the electrou magnetic device, while the average life of a similarl pole shader formed from a copper-beryllium alloy ln accordance with my invention is over 1,600,000 operations of the electromagnetic device. Accordingly, it will be seen that pole shaders constructed in accordance with my invention have a life which is substantially ten times the average life of brass pole shaders heretofore used.

Although my invention is particularly applicable to pole shaders having a bent portion, i. e. pole shaders formed as shown in the drawing, it will be understood that it is applicable generally to pole shaders'oi any shape or size. For example. similar tests are conducted with pole shaders formed from a iiat blank with no bends, i. e. the ears i0 of the pole shader shown in the drawing were omitted and the fiat pole shader was secured in position by other suitable means. Tests of this dat type of pole shader showed that while the average life oi a at pole shader formed of brass is approximately 1,000,000 operations of aoeaiao During the tests of this latter type of pole shader, the pole faces of the magnetic structure were so badly worn that the pole shaders themselves were exposed to the blow of the armature. While some of the shaders formed of an alloy embodying my invention were worn about onethird of the way through, the pole shaders did not break during over 4,000,000 operations of the electromagnetic device.

While I have shown a particular embodiment of my invention) it will be understood, of course, that I do not wish to be limited thereto since many modlcations may be made and I, therefore, contemplate by the. appended claims to cover any such modications as fall withinthe true spirit and scope`oi my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A pole shader formed of an alloy'consisting principally of copper but containing beryllium, said beryllium constituting not more than a few per cent.

2. A pole shader formed of an alloy consisting of about 97 per cent copper, a small percentage of berylliumv constituting not more than l per cent, and the remainder of a metal having the eiective alloying characteristic of cobalt.

3. A pole shader formed of an alloy of about 97 per cent copper, about 2.6 per cent cobalt, and

about 0.4 per cent beryllium.

4. A pole shader formed of an alloy consisting 

